(1) Four different strains of New England white inbred rabbits, the Ax, III/J, III/B and Y strains, were used to study their susceptibility to HVS and EBV, with and without tumor promoting agent (TPA). All the HVS inoculated rabbits developed malignant lymphoma. Both undifferentiated and well-differentiated lymphoma were found which varied with the strain of the rabbits, and the presence or absence of TPA potentiated the initiation of the lymphoma and the degree of lesions. The EBV-inoculated rabbits thus far failed to develop lymphoma, but VCA and EA antibodies were detectable and in some of the rabbits Downey-like cells were observed. (2) Specific transfer factor against Herpesvirus saimiri has been replicated in vitro, inducing the human lymphoblastoid cell line LDV/7. This transfer factor may be useful in prevention or therapy of T cell lymphomas.